1. Field of the Invention
The present invention relates to attaching electrode leads to body implantable devices, such as heart pacemakers and insulin pumps. In particular, the present invention relates to a tool that both connects the lead to the device and seals that connection preventing body fluids from entering therein.
2. Description of the Prior Art
Implantable electric body devices, such as a heart pacemaker an insulin pump, or the like, are well known in the art. In the case of a pacemaker, the device generally includes a pulse generator having a power source, such as a battery and associated electrical circuitry within a sealed protective casing which is substantially inert to body fluids and tissue. The electrical circuitry of the pulse generator is adapted to be connected by a lead or leads to one or more electrodes which are placed in a desired spot within a human body to which electrical pulses to regulate cardiac function are supplied. In an insulin pump, a glucose sensor is connected to the electrical circuitry of the pump to regulate the amount of insulin to be introduced into the body for control of the glucose level.
In the implantation of the stimulator and lead, it is common practice for the surgeon to place the distal end of the lead (which forms the electrode) at the desired spot within a human body and to thereafter connect the opposite end of the lead (which is typically a terminal pin or pins) to a connector assembly associated with the electrical circuitry of the device.
In a pacemaker, the connector assembly includes a terminal block imbedded in an insulating epoxy top and having two bores at substantially right angles to each other. The terminal block is connected by means of an insulated feed-through to the circuitry within the sealed casing. The terminal pin is positioned through one bore and a set screw is inserted into the other bore, thereby clamping the terminal pin against an inside surface of the block and ensuring electrical contact with the lead and the circuitry of the stimulator. To preclude electrical leakage through body fluids, the terminal block must be sealed against the penetration of such body fluids. The electrical lead, typically, has a seal made of a molded ring which is attached to the outer periphery of the lead adjacent the bore and forms a seal when the lead is inserted into the bore, preventing body fluids from seeping therein.
Sealing off the set screw is, however, a somewhat more difficult problem and various methods have been developed in trying to solve this problem. One typical method is illustrated in the Adducci et al U.S. Pat. No. 3,822,707 wherein the terminal pin of the lead is inserted into the connector block and a set screw is inserted in a threaded bore to firmly hold the electrode in contact with a surface on the interior of the connector block. Following the insertion of the set screw, a plug seal is inserted in a separate step to perfect a fluid tight seal. In the Bolduc Patent 3,908,668, a set screw is partly screwed into the connector block and the hole is filled with a grommet having a pair of protrusions. A tool is guided by the protrusions for breaking through the grommet and turning the set screw. The grommet is "self-sealing". However, difficulties arise if the tool does not engage the set screw properly after piercing the grommet in an opertion as delicate as a pacemaker implant. The Kraska et al Patent 4,010,760, shows a similar method of sealing the set screw from body fluids.
The Anderson et al U.S. Pat. No. 4,072,154 uses a set screw and a plug arrangement wherein the set screw is inserted first and the plug later inserted into the opening to effect the seal. The Anderson U.S. Pat. No. 4,180,078 also shows a similar arrangement.
The Richter et al U.S. Pat. No. 4,105,037 illustrates an arrangement where a set screw is first inserted and a "silicone medical adhesive" is subsequently used to fill the opening around the head of the screw.
A further arrangement is illustrated in the Schipko et al U.S. Pat. No. 4,141,752 which discloses a screw for holding the terminal pins of the electrical leads that includes a hard cap surrounding a screw head which is formed from a medical grade epoxy resin. An O-ring around the periphery of the screw head forms a seal to prevent body fluids from seeping to the electrode. One disadvantage that the arrangement of the Schipko et al Patent has is that threshold measurements cannot be made easily once the lead and the stimulator circuitry are connected by the set screw due to the hard epoxy head of the screw.
While all of the above references show arrangements of sealing the set screw, problems in inserting the set screw and sealing occur. The set screw used to connect the electrode to the stimulator is quite small and if a plug is used to seal the set screw, the plug is also quite small. From time to time, one or the other is lost on or near the operating table. In addition, due to their small size, both are quite difficult to handle directly by hand, which is quite undesirable during surgery.